


Underturtles

by CaseyJ0nes



Series: TMNT One Shots [2]
Category: Teenage Mutant Ninja Turtles (TV 2012), Teenage Mutant Ninja Turtles - All Media Types, Undertale (Video Game)
Genre: Gen, One Shot, boys fall into the undertale world, idk i've had it for a while, maybe?? - Freeform, never got back into it, no frisk btw, only up to the first save point tho, the turtles take their place, video game mechanics realized
Language: English
Status: Completed
Published: 2017-07-25
Updated: 2017-07-25
Packaged: 2018-12-06 15:52:02
Rating: Not Rated
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 1,949
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/11603853
Author URL: https://archiveofourown.org/users/CaseyJ0nes/pseuds/CaseyJ0nes
Summary: They had never been lost in the sewers before, at least not this lost, not for a while. And then they were falling into a bed of golden flowers.TMNT/Undertale crossover.





	Underturtles

“Guys, where are we? I’ve never seen this part of the sewers before…”

“What? Do you think we know every bit of it, Leo? It’s a freakin’ big city.”

“We should just get home. Splinter’s going to be wondering where we are.”

“Guys, I _totally_ know where we are. We’re right below Fourth, the way to the lair is like, _right_ down this tunnel.”

Raph stopped in his tracks, causing the other four to stop behind him. “Well, I don’t think we’re gonna be getting down this tunnel unless one of you learned how to fly recently.” The other three looked down and saw the large hole at their brother’s feet, stretching right across the tunnel and at least twenty feet down it.

Leo looked over the side, trying to keep a bit of distance. “I don’t even see the bottom of it… Do you think it could be Kraang? They’ve been pretty quiet lately.”

Raph kneeled at the edge, trying to see the bottom. “Maybe they brought one of those worm things back.”

“Didn’t those like, shake the crud out’a the city last time?” Mikey asked, looking over Raph’s shoulders.

“Maybe it’s one of the holes they left then...” Leo tried again.

“Maybe we shouldn’t get too close to it. It might not be structurally secure around the edges.” Donnie finally spoke up. “You guys could fall in, and Merlin knows where it leads or how deep it is.”

“Donnie, stop worrying. I think we should come back with some gear and see how far it-” Raph cut off at the sound of cracking, and only had time to turn and grab Leo’s hand before he was falling.

Leo, not ready for the added weight, fell towards the hole, only being cut short by Mikey grabbing his feet, who in turn slid towards the edge and was grabbed by Donnie.

“I _told_ you so.” Donnie bit out, struggling to keep Mikey from falling in.

“You know, Donnie,” Raph yelled up to him, his voice echoing off the walls of the hole and sewers, “’I told you so’ has a brother. His name is ‘Shut the hell up and start pulling us out!’”

Donnie started to try and pull them back, only to be stopped by more cracking, as the ground started to break away from underneath Mikey.

As Mikey started sliding down, unable to stop himself, Donnie started panicking, struggling to pull them back up.

“No, no, no! I can’t hold all of you up!” He shouted as he started being dragged in by Mikey. He gave one last attempt before Mikey fell off the edge, and he was dragged down after them.

 

When Leo finally came to, he let out a low groan before opening his eyes and pulling himself into a sitting position.

He blinked a few times before looking up, and seeing the hole in the ceiling very, _very_ far above them. He turned his eyes back down, turning to see all three brothers, all at their own stages of waking up, Mikey rubbing his eyes, Raph still lying on his back and staring up at the ceiling and Donnie sitting on his knees, looking down at the bed of golden flowers they were laying in.

Leo looked down at them himself, reaching down to feel the petals of one. They were soft, and by the lack of pain Leo was in, it was almost like they had cushioned their fall from however high they fell.

“Where are we?” Mikey asked, finally looking around the long, stone room.

“The sewer tunnels?” Leo questioned.

“I don’t think so,” Donnie said, holding a flower in front of his face. “How do they grow?”

“What are you talking about?” Raph asked, now sitting up.

“The flowers.” Donnie clarified, spinning it between two fingers close to his face, then looking up towards the ceiling. “How do they grow? There’s no sunlight, no rainwater, but they’re as healthy as any normal flower, maybe even more so. They’re almost glowing.” He held the flower right in front of his eyes, the golden glow accentuating the red in his usually rust coloured eyes.

“What does it matter?” Raph questioned again.

“Well, usually flowers grow through photosynthesis, which involves a heavy dose of sunlight which it would not get this far underground. Even if it was the kind of flower to bloom only in dark spaces it still wouldn’t be able to get the water or nutrients it needs to thrive. So, with this information, I can only draw up the conclusion that we are _definitely_ _not_ in the sewers of New York.”

“Then… _Where are we_? We fell down a hole in New York!” Leo exclaimed.

“We fall into all kinds of weird crap, it’s not like this is the first time. Let’s stop sitting around and find a way out of here.” Raph suggested.

“We have no idea where we are, we can’t just rush into things.” Leo told him.

“Well, we can’t just sit here!”

“Why don’t we go through that door?” Mikey suggested, pointing to the end of the room.

The three older siblings looked behind them, seeing the dark doorway, leading into an even darker room.

“I don’t think that’s a good idea…” Leo said again, though he got up with his brothers.

“Well, Raph is right, Leo. We can’t just sit here, and we can’t fly, as pointed out earlier, so our only way is through here,” Donnie had moved towards the doorway, trying to see through the darkness. “Wherever _here_ is…”

“Then let’s go.” Raph decided, walking through.

Mikey turned to Donnie, who followed Raph, then turned to Leo and shrugged, following the others through as well.

Leo let out a loud groan before walking through the doorway as well.

The hall was dark, but after a few moments they came to a larger section, with one patch of light sitting in the middle, and in the middle of that, a large, golden flower.

“Does that flower have a face?” Raph asked blatantly.

“ _Well_ , you’re not from around here, _are you_?” The flower spoke, and all four brother’s jumped, staring at it incredulously.

“Did that flower just _talk_?” Donnie asked.

“I did talk, actually. Howdy! Names’ FLOWEY. FLOWEY the FLOWER. And like I was saying, you’re not from around here, are you?”

“Where- Where is _here_ , exactly?” Donnie questioned, Mikey leaning down to see the talking flower better.

“You’re definitely new then. This is the UNDERGROUND. Golly, you must be so confused. Someone ought to teach you how things work around here! I guess little old me will have to do. I’m sure it will work. You may _look_ like MONSTERS but your SOULS feel HUMAN enough.”

The four turtles look offended at the word monsters, and Leo could only ask; “What are you talking about?” before the world blinked in and out of darkness, and suddenly everything looked different. They were stood in a small room, looking down at a box with four hearts sitting in it. One blue, one red, one purple and one orange.

Behind them were three walls, but they looked they were non-existence, just eternal darkness, the illusion only crushed by Donnie pressing his hand against the back wall.

Flowey sat across from them, on the other side of the room.

“See those hearts? They are your SOUL, the very culmination of your being. Your SOUL starts off weak but can grow strong if you gain a lot of LV. What’s LV stand for? Why, LOVE, of course. And judging by those weapons you wear, I’m sure you already have lots of LOVE, but I’ll share some with you anyway!”

The boys looked down at their weapons, Donnie turning to give Raph a confused look.

“Down here, LOVE is shared through. . . Little white. . . ‘friendliness pellets.’ Are you ready? Just think to move your hearts around and try to catch as many as you can!”

White pellets appeared around Flowey, ready to shoot towards the boy’s _souls_.

“I don’t trust this,” Leo said but noticed that he could move the blue heart with just a thought.

“Yeah, he’s too nice.” Raph agreed.

“I don’t understand what’s going on. Where _are_ we?!” Donnie asked, looking around the small box.

“Guys, it’s a talking _flower_. How can you not dig that? He’s just tryin’ to share the love!” Mikey smiled.

“Don’t touch them.” Leo ordered.

“Ready?” Flowey asked, and the pellets started moving towards their hearts.

Leo and Raph immediately moved their hearts out of the way, while Mikey went towards them, and Donnie, distracted by trying to figure out how the box worked, stayed where he was.

As the pellets hit the hearts, Donnie and Mikey cried out in pain, dropping to their knees.

Leo and Raph jumped to their brother’s sides, trying to hold them up before they hit the ground completely. They all looked back to the Flower, now with a wicked smile on his face.

“ _You idiots_. You should have listened to the others. In this world it’s _kill or BE killed._ Why would ANYONE pass up an _opportunity like this?!”_

His smiled turned downright evil as bullets surrounded the box where their hearts were, spinning around them. Raph leant Donnie up against Leo before jumping up to bang at the opening, finding himself stuck inside by an invisible barrier.

“ **Die.** ” The flower said as the bullets started moving towards them at a slow pace, laughing madly. They all moved their hearts towards the centre, trying to avoid the bullets for as long as they could.

And then, as quickly as they appeared, they were gone. The flower looked confused before he was shot out of the box, and a new creature appeared. She looked almost like a goat, though she stood as a human, and their thoughts immediately jumped towards mutant.

With her appearance Donnie and Mikey let out deep gasps, breathing deeply now that the pain was gone.

“What a terrible creature, torturing such poor, youth. . .” She said, in a soft, kind voice. She gave a sad smile at their looks of distrust, helping the now healed brothers to their feet. “Ah, do not be afraid, my children. I am TORIEL, caretaker of the RUINS. I pass through this place every day to see if anyone has fallen down. No one has fallen in quite some time, and certainly no one quite like you four. You almost look like you could be from WATERFALL, but your souls are so clearly human.

“Either way, come! I will guide you through the catacombs.”

The world faded again and when their sight came back they found themselves standing back in the room where they had first seen the flower.

The goat women stood in front of them, before gesturing them to follow and made her way to the other side of the room.

The boys exchanged looks before Leo shrugged, and started to follow her, the other three not far behind.

“Are you sure we can trust this one?” Raph asked.

“No, I’m not sure. But there’s something about her. Something that just feels like we should.” Leo replied as they walked through the door and into a lit room. Purple stone walls surrounded them, and at the end of the room was a pile of red flowers and a sparkling light in front of them.

Mikey walked towards it, and just as he got close enough to touch it, a voice loomed in their heads.

**(The shadow of the ruins looms above, filling you with determination.)**

**(HP fully restored.)**

**{File saved.)**

The boys all stood silent for a moment before Donnie spoke.

“File saved? Are we in a video game?!”

**Author's Note:**

> Idk, I've had this for like a year. If you like it I might continue it. Comment, I guess?


End file.
